Lipozyme TL 100L的固定化及其催化合成蔗糖-6-乙酯

采用树脂吸附法固定脂肪酶Lipozyme TL 100 L,并用于催化合成蔗糖-6-乙酯（S-6-a）。比较7种树脂对Lipozyme TL 100 L的吸附与固定化酶合成S-6-a能力,选择非极性大孔树脂HZ-802为固定化载体。固定化酶在吸附温度30 ℃,蛋白吸附量50.47～58.1 mg/g树脂,相对水含量小于5%时,S-6-a产率达80%以上。用异丙醇以体积比0.5∶1处理Lipozyme TL 100 L,固定化酶的S-6-a产率可达95.4%。固定化酶反复使用8次,S-6-a产率仍有34.2%。与商品固定化酶Lipozyme TLIM相比,HZ-802吸附法制备的固定化酶催化转酯反应的活化能降低了6.47 kJ/mol。     

Solvent-free glycerolysis catalyzed by acetone powder of Nigella sativa seed lipase

The solvent-free glycerolysis of used sunflower oil catalyzed by acetone powder of Nigella sativa seeds was investigated. The highest partial acylglycerols yield was obtained at 60°C. The glycerolysis reactions, conducted at molar ratios of 1:1, 2:1, and 3:1 of oil to glycerol keeping the acetone powder content at 30% based on oil weight and the temperature at 60°C, approached equilibrium after 2 h. The highest partial acylglycerol content of the products was 66% (1:1 molar ratio) and 60% (2:1 molar ratio).     

Solvent-free glycerolysis catalyzed by acetone powder of Nigella sativa seed lipase

The solvent-free glycerolysis of used sunflower oil catalyzed by acetone powder of Nigella sativa seeds was investigated. The highest partial acylglycerols yield was obtained at 60°C. The glycerolysis reactions, conducted at molar ratios of 1:1, 2:1, and 3:1 of oil to glycerol keeping the acetone powder content at 30% based on oil weight and the temperature at 60°C, approached equilibrium after 2 h. The highest partial acylglycerol content of the products was 66% (1:1 molar ratio) and 60% (2:1 molar ratio).     

Analysis of neutral lipids and glycerolysis products from olive oil by liquid chromatography

A simple method was developed to separate model triglycerides, 1,3-diglycerides, 1,2-diglycerides, monoglycerides and free fatty acids and products generated in enzymatic glycerolysis of olive oil by high-performance liquid chromatography with a laser light-scattering detector. The separation was carried out with a silica column at 30°C. A gradient elution with mobile phase A (hex-ane/chloroform/formic acid) and mobile phase B (hex-ane/acetone/chloroform) can separate the compounds into distinct peaks in less than 20 min.     

Repeated use of immobilized lipase for monoacylglycerol production by solid-phase glycerolysis of olive oil

By using immobilized lipase for production of monoacylglycerol (MAG) by solid-phase glycerolysis of fats and oils, the enzyme could be recovered easily from the reaction mixture and recycled to reduce the cost of the catalyst. Several support materials (CaCO₃, CaSO₄·2H₂O, Ca₂P₂O₇, and Celite) were screened for immobilization of Pseudomonas sp. lipase by adsorption and tested for solid-phase glycerolysis of olive oil. Immobilization made the reuse of enzyme feasible. CaCO₃ proved to be the best support: 90% MAG (wt% in the glycerolfree reaction mixture after 72 h of reaction time) was obtained until the fifth use, 80% after the seventh use, and 60% after the tenth use. The same support was found suitable for immobilization of two other bacterial lipases from Chromobacterium viscosum and Pseudomonas pseudoalkali.     

Synthesis of monoglycerides by glycerolysis of rapeseed oil using immobilized lipase

Reaction conditions for the synthesis of monoglycerides (MG) by enzyme-catalyzed glycerolysis of rapeseed oil using Lipozyme® IM have been studied. Silica gel was used to adsorb the glycerol to overcome the problems of low glycerol solubility in the organic phase. An experimental design was used where temperature, time, the ratio of silica gel to glycerol (w/w), the water activity (a) _w , the isooctane concentration, and the ratio of glycerol to triglycerides (mol/mol) were varied. Response surface methodology was used to evaluate initial reaction rate and yield for the different products. The best yield of MG achieved under the studied conditions was 17.4% (mol fatty acid in substance/total mol fatty acid in mixture) (75°C, 20 h, silica gel/glycerol 2:1, a _w =0.17, 48% isooctane, glycerol/triglycerides 6:1). The same conditions yielded 36.8% diglycerides, 13.6% free fatty acids (FFA), and 36.9% triglycerides. This is at the same level as the equilibrium yield. The yield of MG is low compared to the final yield achieved with solid-phase glycerolysis. However, in solid-phase glycerolysis the reaction mixture becomes solid, and therefore the solid-phase process is not suitable for industrial application. The formation of FFA was very fast compared to the synthesis of MG. Equilibrium for FFA was reached within 2 h, and the yield was strongly affected by the a _w . Increasing a _w greatly increased the formation of FFA. In the a _w ratio 0.06–0.3, the yield of FFA increased from 4 to 19% while the yield of MG was nearly unaffected. As FFA is an undesired product, it is important to keep the a _w as low as possible.     

Biocatalytic production of ricinoleic acid from castor oil: augmentation by ionic liquid

Abstract

In present study involving castor oil hydrolysis catalyzed by porcine pancreas lipase, organic solvent, and ionic liquid were applied to augment production of ricinoleic acid. Toluene was the best organic solvent (30.18% hydrolysis in 2?h). In presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]), an ionic liquid, the optimal conditions were, 0.12?g ionic liquid/g oil, 4?mg enzyme/g oil, 2?g buffer/g oil, pH of 8, and 2.5?h. Under this condition, ricinoleic acid recovery was 43.41 and 52% at 25?°C and 35?°C, respectively. Organic solvent concentration, enzyme concentration, buffer concentration and time had significant impacts on lipase catalyzed hydrolysis in the presence of organic liquid; whereas, pH and speed remained insignificant. In hydrolysis involving ionic liquid, time had most important effect on ricinoleic acid production. Interaction between enzyme and buffer concentration was most significant. Interactions of ionic liquid concentration with all other variables were also significant besides buffer concentration–time interaction.     

Separation of EPA and DHA in fish oil by lipase-catalyzed esterification with glycerol

The objective of this study was to investigate the use of lipases as catalysts for separating EPA and DHA in fish oil by kinetic resolution based on their FA selectivity. Esterification of FFA from various types of fish oils with glycerol by immobilized Rhizomucor miehei lipase under water-deficient, solvent-free conditions resulted in a highly efficient separation of EPA and DHA. Reactions were conducted at 40°C with a 10% dosage of the lipase preparation under vacuum to remove the coproduced water, thus rapidly shifting the reaction toward the products. The bulk of the FA, together with EPA, were converted into acylglycerols, whereas DHA remained in the residual FFA. As an example, when FFA from tuna oil comprising 5% EPA and 25% DHA were esterified with glycerol, 90% conversion into acylglycerols was obtained after 48 h. The residual FFA contained 78% DHA and only 3% EPA, in 79% DHA recovery. EPA recovery in the acylglycerol fraction was 91%. The type of fish oil and extent of conversion were highly important parameters in controlling the degree of concentration.     

A comparative study of mayonnaise and italian dressing prepared with lipase-catalyzed transesterified olive oil and caprylic acid

Viscoelastic properties of mayonnaise and Italian salad dressing prepared with olive oil and enzymatically synthesized structured lipid (SL) from caprylic acid and olive oil were studied using an SR5000 dynamic stress rheometer. Storage modulus (G′) and loss modulus (G″) were determined as functions of frequency, temperature, and stress. Frequency sweeps did not show significant differences between dressings prepared with olive oil or SL. For all mechanical spectra, G′ values were consistently higher than G″ values. Both Italian dressing and mayonnaise samples displayed similar gel-like characteristics. Mayonnaise and Italian dressings made with olive oil separated when they were brought to room temperature from refrigeration temperatures. SL-based mayonnaise did not separate. Only minor separation was observed in SL-based Italian dressing. A change in the crystallization properties of the two oils was probably responsible for the differences observed after refrigeration. Both SL-based and unmodified olive oil-based mayonnaise and Italian dressing samples had similar viscoelastic character.     

粘胶短纤维的干燥特性及其动力学模型研究

分析了热风温度、纤维层厚度、热风速度、纤维层含水率等工艺参数对粘胶短纤维干燥过程的影响,在此基础上,建立了粘胶短纤维的干燥动力学模型,应用单指数干燥模型和Logaritmic干燥模型对比研究了纤维的干燥特性。结果表明:单指数干燥模型和Logaritmic干燥模型都能很好地描述热风温度、纤维层厚度、纤维层含水率对其干燥速率的影响;在计算热风温度以及热风速度对纤维干燥的影响时,两个干燥模型计算结果与实验结果略有偏差;相比单指数模型,Logaritmic干燥模型的计算结果和实验结果吻合较好,能更好地分析粘胶短纤维的干燥规律,对粘胶短纤维干燥特性的工程应用提供理论依据。     

Kinetic study of the curing behavior of bismaleimide modified with diallylbisphenol A

The curing kinetics of bismaleimide modified with diallylbisphenol A were investigated for different ratios of 1,1′‐(methylene di‐4,1‐phenylene) bismaleimide and diallylbisphenol A with differential scanning calorimetry. Multiheating‐rate and isothermal methods were used to study the kinetics of the curing process. The results indicated that the activation energy changed with the extent of conversion. The activation energy obtained by the multiheating‐rate method was higher than that obtained by the isothermal method. Two kinetic models (autocatalytic and nth‐order) were successfully used to model the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2229–2240, 2003     

用离子液体脱除燃料油中有机硫化物的研究

以咪唑类离子液体作为萃取脱硫剂,在正辛烷和甲苯的混合溶液中加入少量的噻吩构成油品模拟体系。采用正交实验,系统考察了单级萃取中温度、时间、剂油比以及离子液体碳数对脱硫效率的影响,得到了较优的脱硫条件:温度约60℃、萃取时间约40 min、剂油比为1∶1、侧链碳数为10。考察了多级脱硫效率以及离子液体的回收利用。结果表明,经过5级脱硫后,燃料油含硫可以达到欧Ⅲ标准,离子液体重复使用5次后,脱硫效率约降低了2%。回归得到了模拟油品中脱除噻吩的萃取动力学方程。该研究为基于离子液体的燃料油脱硫工艺提供了重要的基础。     

Kinetic modeling strategy for an exothermic multiphase reactor system: Application to vegetable oils epoxidation using Prileschajew method

Epoxidation of cottonseed oil by peroxyformic acid (PFA) was studied in a semibatch calorimeter. This liquid–liquid reaction system is composed of different exothermic steps. Thus, a kinetic modeling strategy to diminish the number of parameters to estimate was developed by investigating each reaction system: PFA synthesis and decomposition, ring‐opening and epoxidation. A thermal study was conducted by determining heat capacity of the different organic species, and by analyzing the evolution of global heat‐transfer coefficient with the reaction extent. The epoxidation reaction was performed in a semibatch reactor under isoperibolic mode within an initial temperature range of 50–70°C, an organic phase of 30–34 wt %, a formic acid molar flow rate of 0.02–0.05 mol/min and an addition time of 25–50 min. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlation. Nonlinear regression was used to estimate the kinetic and thermal parameters. The kinetic parameters of epoxidation of the three different fatty acids, namely oleic, linoleic, and its intermediate were estimated. The reaction enthalpy of epoxidation was estimated to ?230 ± 3.8 kJ/mol, and the reaction enthalpy of ring‐opening was measured to be ?90 kJ/mol by Tian–Calvet calorimeter. © 2015 American Institute of Chemical Engineers AIChE J, 62: 726–741, 2016     

Kinetic study of an anaerobic fluidized bed system used for the purification of fermented olive mill wastewater

The anaerobic digestion of olive mill wastewater (OMW) in a fluidized bed, pretreated with Geotrichum candidum, has been studied. The bioreactor used (volume = 3.5 dm³; biomass concentration = 11.5 g VSS dm^?3) maintained satisfactory operation for 4 to 35 days, in terms of hydraulic retention time, and removed 92% of the initial COD. The system was used to develop and test a kinetic model which was subsequently employed to determine growth yield and maintenance coefficient. From the results obtained, the Michaelis-Menten equation accurately described the substrate uptake (i.e. COD removal) in the anaerobic fluidized bed system. Pretreatment of the OMW was found to increase the rate of substrate uptake by a factor of 3.2 when compared to untreated OMW.     

Kinetic modeling of lipase‐mediated one‐pot chemo‐bio cascade synthesis of R‐1‐phenyl ethyl acetate starting from acetophenone

BACKGROUND: A systematic investigation of mutual interference between a hydrogenation catalyst, Pd/Al₂O₃, and an immobilized lipase in a one‐pot synthesis of R‐1‐phenyl ethyl acetate at 70 °C has been undertaken. This paper reports the kinetic modeling of lipase‐mediated chemo‐bio cascade synthesis of R‐1‐phenyl ethyl acetate starting from acetophenone. RESULTS: The kinetic results revealed that these catalysts were not acting independently but in concert. A mechanism which predicts the experimental observations for this reaction is proposed. CONCLUSION: The parameters of the kinetic model, which are in good agreement with the experimental data, were estimated through numerical data fitting. The reliability of the estimated parameters was analyzed using the Markov Chain Monte Carlo (MCMC) method. Copyright © 2009 Society of Chemical Industry     

Kinetic study of the methanol to olefin process on a SAPO-34 catalyst

In this paper, a new kinetic model for methanol to olefin process over SAPO-34 catalyst was developed using elementary step level. The kinetic model fits well to the experimental data obtained in a fixed bed reactor. Using this kinetic model, the effect of the most important operating conditions such as temperature, pressure and methanol space-time on the product distribution has been examined. It is shown that the temperature ranges between 400 °C and 450 °C is appropriate for propene production while the medium temperature (450 °C) is favorable for total olefin yield which is equal to 33%. Increasing the reactor pressure decreases the ethylene yield, while medium pressure is favorable for the propylene yield. The result shows that the ethylene and propylene and consequently the yield of total olefins increase to approximately 35% with decreasing the molar ratio of inlet water to methanol.